Mechanism of pattern formation in polymer ionic liquid blends under the influence of an electric field*

Formation of controllable self-assembled patterns in soft materials can be used to design a variety of multifunctional materials with tunable properties. Here, we utilize unique properties offered by the blends of polymers and ionic liquids (PIL) to reveal the mechanism behind the formation of intricate morphological patterns that emerge in these blends in the presence of an external electric field (EF). In particular, we perform stability analyses to identify key parameters that can be used to lock a pattern of a particular wavenumber in PILs. In addition, we reveal that under the effect of an external stimulus, which in our case is the strength of the EF, both ordered and disordered phase morphologies can co-exist. We also show that the increased strength of EF in PIL system results in the formation of alternating layers of polymer-rich and IL-rich phases of different widths. The reason for this behavior is attributed to cation-anion, polymer-anion, and polymer-cation interactions present in the blends. Thus, the effect of EF can drive new patterns and allows the control of these patterns through wavenumber locking. We believe that our approach can be extended to a variety of soft matter blends containing constituents with stark different properties.